Efficacy of halofuginone lactate in the prevention of cryptosporidiosis in dairy calves.

To evaluate the efficacy of halofuginone lactate (Halocur; Intervet) when used prophylactically against cryptosporidiosis in dairy calves, 513 Holstein heifer calves were randomly distributed between two experimental groups. Those in the treatment group (n=259) received 0.1 mg halofuginone base per kg bodyweight daily in a 10 ml solution, for the first seven days following birth, while those in the control group (n=254) received an equal volume of a placebo solution. Faecal samples were collected weekly from all calves until three weeks of age to test for Cryptosporidium oocysts and to assess the diarrhoeal status. Growth parameters of the calves were also recorded at approximately four months of age. Calves that received halofuginone were significantly less likely to shed Cryptosporidium oocysts during the course of the study than placebo-treated calves (odds ratio 0.6, 95 per cent confidence interval 0.4 to 0.9, P=0.009). Mean growth measurements of calves in the treated group were consistently higher than those of the control calves (hipometer-derived P=0.052, wither height P=0.097) and mortality was lower in the treated group (P=0.07). However, these differences were not statistically significant (P>0.05). No association was found between the prophylactic use of halofuginone and the incidence of calf diarrhoea.

Effect of halofuginone lactate on the occurrence of Cryptosporidium parvum and growth of neonatal dairy calves.

Thirty-one Holstein bull calves were purchased at birth from 3 dairy farms in Eastern Ontario. Each calf was assigned at random to oral treatment with either 5 mg of halofuginone lactate in 10.0 mL of aqueous carrier solution (Halocur, base comprised 10 mg of benzoic acid, 100 mg of lactic acid, and 0.3 mg of tartrazine) or 10 mL of placebo (Halocur base minus the active ingredient, halofuginone lactate) administered 15 to 30 min after morning milk feeding for the first 7 d of life. Intakes of milk, calf starter, and water, and fecal consistency score were recorded daily for 56 d. Calf weights were recorded weekly for 56 d. Fecal samples were taken from all calves at approximately 2, 7, 14, 21, and 28 d of age for isolation of Cryptosporidium parvum oocysts. Logistic and linear regression analyses were used to assess the effect of treatment on the incidence of diarrhea and C. parvum infection status. The odds of C. parvum shedding among calves in the halofuginone lactate-treated group was 70% lower than the odds of shedding among calves in the placebo group. In calves treated with halofuginone lactate, no oocyst shedding occurred until 2 wk of age, whereas 12.5% of calves in the placebo group began shedding oocysts during wk 1. From all ages of placebo-treated calves, 31 of 73 samples (42.5%) were positive for C. parvum, whereas only 15 of 67 samples (22.4%) from all ages of halofuginone lactate-treated calves tested positive. The largest number of C. parvum-positive samples occurred in the third week of life. There was a significant delay of 3.1 d in the incidence of diarrhea among calves treated with halofuginone lactate. Intake of milk and starter, body weight gains, and age at weaning were not significantly different between treatment groups.